Quantitation of host cell proteins in biopharmaceuticals from chinese hamster ovarian and vero cell lines using capillary electrophoresis western blots.

Quantitation of host cell proteins (HCPs) is essential in the process of preparation of many biological and vaccine products. Common methods of quantitation include the widely applied enzyme-linked immunosorbent assays (ELISAs), mass spectrometry (MS) and other orthogonal assays. Prior to using these techniques, critical reagents need to be evaluated, for example, antibodies need to be assessed for HCP coverage. Percent of HCP coverage is often established by denatured 2D Western blot. However, ELISAs measure the amount of HCP only in a native state. There are limited studies linking reagents validated by 2D-Western to ensure adequate coverage in the final ELISA. ProteinSimple's newly developed capillary Western blot technology allows for separation, blotting, and detection of proteins in a semi-automated and simplified format. Capillary Westerns are similar to slab Westerns, with the added benefit of being quantitative. Here we outline the capillary Western method that links the 2D Western coverage and ultimately ELISAs for more efficient HCP quantitation. This study describes the development of the capillary Western analytical method to quantitively evaluate HCPs in Vero and Chinese Hamster Ovarian (CHO) cell lines. The amount of CHO HCPs decreases as the sample is purified as expected. Using this approach, we determined that the detected Vero HCPs amount was similar irrespective of denatured (capillary Western) versus native assay format (ELISA). This new method can also be potentially employed to quantitatively assess the anti-HCP antibody reagent coverage used in commercial HCP ELISA kits.